Computing device



J n 12, 1951 R. G. MURDICK ET AL COMPUTING DEVICE Filed Nov. 3, 1950 t Wmdm Va ri able P/ v Ihventors: Robert G. Murdick, Alexander (3. Robbins,

Their- Attorneg.

Patented June 12, 1951 UNITED STATES PATENT OFFICIE COMPUTING DEVICE Robert G. Murdick and Alexander G. Robbins,

Schenectady, N. Y., assignors to General Electric Company, a. corporation of New York Application November 3, 1950, Serial No. 195,690

3 Claims. 1

This invention relates to computing devices and more particularly to D.-C. resolvers in which positive and negative values of the sine and cosine of an input angle are continuously indicated in terms of an electric current or voltage.

An object of this invention is to provide a new and improved device for computing electronically the positive and negative values of the sine and cosine of an angle through which a shaft rotates.

Another object of this invention is to provide a new and improved D.-C. resolver having a highly accurate output which is substantially unaffected by changes in the load.

A further object of this invention is to provide a new and improved D.-C. resolver suitable for gauging to a plurality of similar resolvers.

For further objects and advantages and for a better understanding of this invention, attention is now directed to the following description and accompanying drawing and also to the appended claims. The drawing is illustrative of a D.-C. resolver constructed according to this invention.

Referring to the drawing, a pair of non-linear resistance cards I and 2 are provided with variable pitch windings Ia and 2a. Windings Ia and 2a are mounted on notched or irregularly shaped winding supports Ib and 2b. The notched supports and the variable pitch windings effect a nonlinear resistance card which is further described hereinafter. The notches in cards I and 2 are such that each of the cards is substantially a half ring. Cards I and 2 are mounted in juxtaposition in the same plane to form a substantially closed ring. Windings Ia and 2a are electrically connected together at adjacent ends of cards I and 2 and the center taps of the windings are electrically connected to ground. Sources of equal positive and negative voltage are connected to opposite ends of windings Ia and 2a. A rotatable shaft 3 is located transverse to the principal plane of the ring formed by cards I and 2 and passes through the center of rotation of the ring. Mounted on shaft 3 is a star-shaped bracket 4 having four extensions mutually perpendicular to the longitudinal axis of shaft 3 and spaced 90 degrees apart. Bracket t is a support for four identical brush assemblies utilized in deriving quadrature voltage signals from cards I and 2. For convenience, only one of these assemblies is described herein.

A resilient electron conducting brush holder 5 is mounted on an extension of bracket 4 and supports an electrical contact brush 6'. Bracket 4 is so positioned on shaft 3 that rotation thereof causes brush 6 to wipe on windings Ia and 2a along a, circular track I. A contact brush 8 is supported by a brush holder 9 mounted on the back side of the extension of bracket 4. This brush wipes on a slip ring I0 which is connected through a load resistor II to ground. Windings Ia and 2a are generally formed of insulated wire and the insulation along track I is removed. The insulation is removed only from the exposed portion of the windings after the cards have been wound. Short-circuiting between turns is thus prevented. Resistance cards I and 2 are separated by grooves which may damage the brushes as they wipe thereon. Also, the windings may be damaged at these points of irregularity. Resilient members I2 and I3 positioned between the irregularities between cards I and 2 and bracket 4 intercept brush holder '5 as it is rotated thereby. Members I2 and I3 raise the brushes from track "I at the irregularities between the cards and thereby prevent damage to the windings or to the brushes. Small nipples l4 and I5 are provided near the ends of members I2 and I3 to effect easy passage of the brush holders thereacross. Members I2 and 13 are formed of a conducting material and also serve as terminals whereby the heretofore mentioned direct voltages may be supplied to opposite ends of windings Ia and 2a. Because members I2 and I3 are connected to the ends of the windings, no electrical discontinuity is introduced thereby.

In operation shaft 3 is rotated and the magnitudes of the voltages across the load resistors are indication of different trigonometric functions of the angular position of the shaft. Because there is only one brush on any card between a voltage and ground at any one time, the cards may be tapered and irregularly wound to compensate for the resistance load to give a voltage proportional to sin 0, cos 0, sin 6, and cos 0 at different brushes. The load resistors are made equal so that the compensation of each card is the same for all of the brushes. Consequently, the output voltages for the different trigonometric functions are simultaneously and continuously obtained. The resistance of the windings between the center tap and any point on the card is given by the following equation:

a=ratio of load resistance to the resistance of the card between the source of voltage and ground.

ac=fractional resistance between the brush and ground.

f=ratio of the distance between the brush and ground to the distance between the end of the card and ground.

Although this device finds particular application in computers requiring highly accurate and sensitive resolvers,-it isalso useful inlless sensitive apparatus. Because it is ring-shaped, it lends itself to ganging while being very compact. In the present state of the art, the width of nonlinear resistance cards is limited, and, therefore, this card has the further advantage over the square prior art type cardsin'thatjgreaterresolm tion per card is obtained.

Modifications of this invention will occur to those skilled in the art and itiszdesired .toxbe .understood, therefore, that this invention is not to be limited to the particular embodiment disclosed, .but that the appended claims are meant to cover iallth'emodifications which are within the spirit andscope of this invention.

Wh'at'we claim'as new-and desire to secure by LetterslPatentofthe United States is:

21. 'InaD.-C;'resolver,'.a' pair of nonlinear resistance cards,.said resistance'cards'being formed in theshape of semicircular rings and being positioned in-the same. plane'to form a substantially circular ring, adjacent ends of said resistance cards being electrically-connected together, and .the'center'taps thereofv being connected to ground,

..a shaft locatednormtl .tolthe principal plane of andthrough the center of saidring, a bracket fastened to.said shaft to-be rotated .thereby, a number of-extensions on said bracket, said extensions being spaced90 degrees apart and the plane thereof paralleling the 'principal plane of said resistancecards, contact means mounted on each: of 'said extensionsto wipe on said resistance cards-throughout a substantially complete rotation of said shaft, resilient conducting means .positioned at .thejunction'of said. resistance cards to lift saidconta-ctmeans from said resistance cards "as they ipass theijimction point thereof, 1 :said resilient conducting means beingelectrically connected to theends of said: resistance cardsad- ;-jacent thereto, sourcesof'equal positiveiand-negative direct voltages L'connected 'toopposite ends of .said resistancecards, aLnum'ber of equal valued .load resistors, .and contact means connected to .provide across each of said lead resistors from .onefof. said contact means a di'ii'erent voltage hav- -ing aLmagnitude :which is a trigonometric "func- :tion of the angular-position of said shaft.

2. In a D.-C. resolver, a. pair of nonlinear resistance cards, said cards formed in the shape of semi-circular rings and having variable pitch windings, said resistance cards being mounted in the same plane to form a substantially circular ring, adjacent ends of said resistance cards being electrically connected together and the center taps of ='each-aofisaid resistance cardsi'being connected togroun'd, a. rotatableishaftlocated normal to the principal plane of and through the :..center of said ring, contact means connected to be rotated by said shaft about the faces of said resistance cards, equal valued resistors connected .betweenggroundzand each of said contact means, and sour.ce::.oiwequal positive and negative Voltages connected to opposite ends of said resistance cards .toprovide-across each of said load resistors a voltage'having a magnitude proportional to the angular position of said shaft.

3. A D.-C. resolver comprising first and second .cardelike insulating :members, conducting Wire being Wound around -:the shorter dimension of each of :said cards; said cards being notched along -.the entire length suchthat the length of the ordinate=of-saidcard corresponds to a function of the abscissa thereof, said notching proj ectinginto said card at -the center and'along the outerportion at the ends thereof, said cardszthereby being substantially in the shape of 'half'rings, said cards being-fastened togetheninthe same plane to substantially form a complete ring, said .windings on saidcards :being electrically connected at adjacent ends of said cards,fthewindings at:.the:center of said cards being. grounded, :a source of positive direct voltagebeing' connectedto the wind- :ingsat one end "of said cards and a-source of equalinegativexdirect voltage being connected to the windings at .the other :end of said cards, a shaft: located irr'a planethrough' the center of the ringrformed bysaid: cardsland normal to the ma- ;jor plane of tsaid cards, .contact means connected to :said: shaftzto be'rotatedthereby about the cir- .cumference 'ofsa 'circleaof tdeterminable radius, said contact zmeans cbeing positioned along said shaft to brush on said windings as said shaft is -rotated,.and;loading resistors connected between saidcontactmeans and groundftoprovide a volt- .age across 'each resi'stor which is :proportional to *a=.trigonometric function Tofithe angular position :of said :sha'ft.

ROBERLT .G. MURDICK. ALEXANDER Gr. ROBBINS.

No references cited. 

